Hi, between sessions. if the user tries to change the clock in order to go through some security code that grants access only for 6 months. Our software is actually free, we just do this in order to make sure that the user is using the latest version, because we get many complaints of users that are using prehistoric versions of the software and did not even bother to update.
I am not aware of an API function that can do this, but you can easily store the current date/time in your application settings (when the users exits the program) and compare it to the current date/time the next time your application starts.
In fact I am doing that right now, comparing last valid date with current date. Thanks a lot for the help and the information regarding this impossibility!